The invention relates to cold start fuel enrichment circuitry for a two cycle internal combustion engine, and to a combined cold start and knock prevention circuit.
During starting and while the engine is cold, a richer fuel-air mixture is desirable. Various enrichment circuits are known in the art. The present invention provides further improvements in such circuitry.
The invention further facilitates combination with knock prevention circuitry and with fuel control circuitry in the above noted co-pending applications. Premature firing of the fuel-air mixture in the combustion chamber of an internal combustion engine causes the mixture to explode rather than burn smoothly. This phenomena is called knock or detonation, and results in loss of power and possible engine damage. Knock becomes more severe with lower fuel octane rating. It is known in the art to sense knock with an audio transducer mounted to the engine, and to reduce knock by supplying a richer fuel-air mixture, U.S. Pat. Nos. 4,243,009 and 4,667,637, incorporated herein by reference.